1. Field of the Invention
The invention relates to an epitaxial substrate, a semiconductor light-emitting device using such epitaxial substrate and fabrication thereof, and more in particular, to an epitaxial substrate having hetero-nanorod, a semiconductor light-emitting device using such epitaxial substrate and fabrication thereof.
2. Description of the Prior Art
The compound semiconductor materials, such as GaN, AlGaN, AlInGaN, and other III-V group compounds, or CdTe, ZnO, ZnS, and other II-VI group compounds, have been used for a wide variety of substrates of microelectronic devices including transistors, field emission devices, and optoelectronic devices, but not limiting the above described.
Taking GaN-based microelectronic devices as an example, a major problem in manufacture is that the GaN semiconductor layer manufactured must have low defect density to ensure the performance of GaN-based microelectronic devices. It is understood that one of these contributors for defects is the lattice mismatch between the substrate and the GaN layers grown on the substrate. So, though the GaN layer has been grown on the sapphire substrate, but it is well known that the GaN layer is preferably grown on the AlN buffer layer previously formed on the SiC substrate to reduce the defect density, especially to reduce the density of threading dislocations. Though there are these considerable progresses, it is still the goal wanted to reach to reduce the defect density continuously on the research.
It is also well-known that the condition of epitaxy is controlled to achieve the lateral epitaxy by use of the substrate with patterned surface, which benefits in preferred orientation of epitaxy, to reduce the defect density or control defects. For example, a GaN semiconductor layer can be formed on the sapphire substrate with patterned surface in lateral epitaxial way to control dislocations in extending laterally to reduce the density of threading dislocations.
However, the prior arts regarding manufacture of the epitaxial substrate with patterned surface all utilize a photolithography process. Obviously, the prior arts regarding manufacture of the epitaxial substrate with patterned surface have high manufacture cost and slow production speed.